Beauveria bassiana is a fungus which causes a disease known as the white muscadine disease in insects. When spores of this fungus come in contact with the cuticle (skin) of susceptible insects, they germinate and grow directly through the cuticle to the inner body of their host. Here the fungus proliferates throughout the insect’s body, producing toxins and draining the insect of nutrients, eventually killing it. Therefore, unlike bacterial and viral pathogens of insects, Beauveria and other fungal pathogens infect the insect with contact and do not need to be consumed by their host to cause infection. Once the fungus has killed its host, it grows back out through the softer portions of the cuticle, covering the insect with a layer of white mold (hence the name white muscadine disease). This downy mold produces millions of new infective spores that are released to the environment.
Beauveria is a naturally occurring fungus in soils throughout the northeast (and the world!) and has been researched for control of soil borne insects (e.g. the May beetle in Europe, the Argentine stem weevil in New Zealand). Many soil insects, however, may have a natural tolerance to this pathogen, which is not exhibited in many foliar pests. Therefore, commercial development of this fungus for biological control has primarily been targeted against foliar feeding pest,.
Current commercial formulations are limited to those produced by two companies:
- Mycotech Corp. in Butte, MT, Laverlam International Corp.
- Mycotrol®, Mycotrol 0®, BotaniGard®ES, BotaniGard®22WP
- Troy BioSciences in Phoenix, AZ
All are foliar formulations of the spores of the fungus, and as the spores are microscopic, can be applied with standard spray equipment. BotaniGard®22WP can also be used as a dip for cuttings, and for soil applications – landscape and containers.
BotaniGard®ES is registered for whitefly, aphids, thrips, mealybugs on Vegetables, Fruits and Berries, Herbs and Spices, Ornamentals, Turf & Forestry.
BotaniGard®22WP is registered for whitefly, aphids, thrips, psyllids, weevils, and mealybugs in Ornamentals and Vegetables, Indoor/Outdoor Nurseries, Greenhouses, Commercial landscape/Interiorscape, and Turf.
Mycotrol® is registered for whitefly, aphids, thrips, mealybugs, leathoppers, weevils, and leaf-feeding insects in Agronomic, Vegetable, and Orchard Crops.
Naturalis®L is registered for mites, thrips, whitefly, aphids, caterpillars, mealybugs, fungus gnats, and shoreflies in Greenhouses and on Ornamentals, Vegetables, Fruits and Herbs.
Beauveria products are reduced risk pesticides. Even so, applicators should wear
- long-sleeved shirt and long pants
- shoes plus socks
- dust/mist filtering respirator (WP formulation)
- waterproof gloves
- goggles (ES formulations)
Restricted entry interval (REI) -4 (ES) or 12 (WP) hrs.
Preharvest Lnternval – 0 days (exempt from residue requirements)
Environmental safety is good. These products are generally non-toxic to beneficial insects, however, applications to areas where bees are actively foraging should be avoided. Beauveria products should not be applied to water, as they are potentially toxic to fish.
The start and frequency of application varies with the pest and their susceptible life stages. In all cases, insect monitoring programs should be in place. For greenhouse management, it is recommended that treatment begin as soon as the insect pests are detected. In potatoes in northern Maine, we initiate treatments when thresholds of 1.5 larvae per plant are exceeded.
Phytotoxicity has been minimal, but a small sample of targeted plants should be checked. After mixing with water, Beauveria products should be sprayed as soon as possible, as fungal spores die and material loses its viability overnight. The foliage should be sprayed until the plants are wet thoroughly, but not to run-off. Equipment that gets the material to the undersides of the leaves will result in prolonged activity, as spores are inactivated by sunlight. Evening applications may be desirable.
The frequency of applications also depends on the pest and the crop. For greenhouse pest problems, applications every 5-7 days are recommended. Again, all applications should be based on monitoring of pest populations.
The rate at which Beauveria spores kill their host is dependent on temperature. At a constant 72 oF, small potato beetle larvae are killed in 3-5 days. Under field conditions in Maine, it may take 7 to 10 days to kill larvae.
Compatibility with other pesticides
Beauveria products should not be tank-mixed with fungicides. Fungicides should not be applied within 24 hours of Beauveria applications. (An exception maybe copper hydroxide.) Beauveria products are compatible with a number of adjuvants and chemical and biological insecticides. But, as Beauveria products contain live organisms, some chemicals may have detrimental effects, and growers should contact the specific manufacturer or dealer for specific recommendations. Imidacloprid appears to synergize the activity of Beauveria for several pest insects, including potato beetles.
Beauveria and Bt for control of Potato Beetles
We have found the combination of Bt products with Mycotrol® to provide an effective management strategy for the Colorado potato beetle in northern Maine. This program provided as effective, if not better management of potato beetles than conventional insecticides, and frequently required fewer applications. The reduction in the number of second-generation adults following Beauveria treatments is thought to be due to the transmission of the disease from dead larvae (those that die as a result of foliar applications) to pupae and adults that contact the spores from the larval cadavers on the soil surface.
The cost of this management program currently exceeds that of many of the available insecticides for non-organic growers. Our current research focuses on potential strategies for managing long-term suppression of potato beetles with Beauveria. If a Beauveria management program provides long-term pest suppression, the cost may be competitive over the long run.
By: Ellie Groden, Associate Professor of Entomology, Dept. of Biological Sciences, 306 Deering Hall, University of Maine, Orono, ME 04496, (207) 581-2984
Originally published: Proceedings. 1999. New England Vegetable and Berry Growers Conference and Trade Show, Sturbridge, MA. p. 313-315.
Updated : T. Jude Boucher, UConn IPM, 2012
Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
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